The present invention relates to a rotary compressor, and more particularly to a rotary compressor suitable to a compressor using hydrofluorocarbon (HFC) refrigerant.
A longitudinal sectional view and a lateral sectional view of a conventional rotary compressor are shown in FIG. 12 and FIG. 13. In FIG. 12 and FIG. 13, a motor unit 2 and a compressor unit 3 are disposed inside an enclosed container 1. A shaft 4 is directly coupled to the motor unit 2. The shaft 4 is supported by a main bearing 5 and a subsidiary bearing 6 provided above and beneath the compressor unit 3. A cylinder 37 is provided concentrically with the shaft 4. In the compressor unit 3, a suction hole 8 is formed in the side of the cylinder 37, and a discharge notch 9 is formed in the upper part of the cylinder 37. One end of a suction pipe 10 is connected to the suction hole 8. A discharge port 11 is formed in the upper part of the enclosed container 1. One end of a discharge pipe 12 is connected to the discharge port 11. Other end of the suction pipe 10 and other end of the discharge pipe 12 are connected to an accumulator (not shown). As lubricating oil, refrigerating machine oil 27 is added to the refrigerant. The refrigerating machine oil is liquefied in the enclosed container 1.
In this structure, the refrigerant circulates inside and outside of the enclosed container 1.
A roller 33 is installed in the cylinder 37, eccentrically to the shaft 4. The roller 33 makes a planetary movement along with rotation of the shaft 4. Between the suction hole 8 and the discharge notch 9 in the cylinder 37, a guide groove 34 is formed in the radial direction of the cylinder. A flat vane 35 is inserted in this guide groove 34. By thrusting force and back pressure (discharge pressure) of a spring 16, the vane 35 is pressed against the roller 33 at the axial center side of the cylinder 37. Thus, the space in the cylinder 37 is partitioned into a suction chamber 17 and a compression chamber 18.
In this structure, the roller 33 makes a planetary movement along the inner wall inside of the cylinder 37. As a result, the vane 35 pressed against the outer wall of the roller 33 moves in and out in the radial direction of the cylinder 37 inside the guide groove 34. In the suction chamber 17 partitioned by the vane 35, gas is sucked in through the suction port 8. The sucked gas is compressed in the compression chamber 18, and this gas is discharged into a specified space through the discharge notch.
Generally, the manufacturing method of the vane 35 comprises a step of heating a special ferrous fusible material having an excellent wear resistance, a step of grinding after heating, and a step of nitriding for forming a nitrogen diffusion layer and a compound layer. In this case, the compound layer at the leading end of the vane 35 is left over, and the vane side rubbing against the cylinder 37 is ground and finished precisely to enhance the dimensional precision.
However, since the nitrogen diffusion layer of the vane side exposed by precision finishing is a single layer, the conventional vane 35 cannot hold the refrigerating machine oil. As a result, the cylinder 37 and vane 35 are slightly inferior in wear resistance. In addition, since the vane 35 is made of special ferrous fusible material, entire surface processing is needed. Hence, the manufacturing cost is very high.
Recently, on the other hand, the sliding conditions are very severe in the cylinder 37, roller 33, and vane 35. Still more, when R22 (monochlorodifluoromethane) substitute refrigerant is used as the refrigerant, combination with a material having a higher wear resistance is required. That is, as in the conventional vane 35, the wear resistance is insufficient in the vane 35 made of a single material such as special steel, special casting, or ferrous sintering material. Further, if the vane 35 made of such special ferrous fusible material is processed by finishing or nitriding, sufficient wear resistance is not obtained in the cylinder 7 or vane 35.
It is hence a primary object of the invention to present a rotary compressor having an excellent wear resistance and low cost.
A rotary compressor of the invention comprises:
(a) a cylinder having an inner space and a groove,
(b) a roller sliding along the inner surface of the inner space of the cylinder,
(c) a vane inserted in the groove, and
(d) a refrigerant.
In which the groove penetrates through the outside of the cylinder and the inner space, and the vane slides in and out in the groove while sliding on the roller.
The vane includes sintered stainless, nitrogen diffusion layer disposed on the surface of the sintered stainless steel, and a compound layer of iron and nitrogen disposed on the surface of the nitrogen diffusion layer.
The sintered stainless steel has a plurality of fine pores formed by sintering of the powder material, and the plurality of fine pores have a porosity of 15% or less.
Preferably, the vane includes stainless steel of martensitic structure, a nitrogen diffusion layer disposed on the surface of the stainless steel, and a compound layer of iron and nitrogen disposed on the surface of the nitrogen diffusion layer, and more specifically, the stainless steel has one chemical composition of either
(i) a chemical composition of iron, 9 to 27% of chromium, and 0.4% or more of carbon, or
(ii) a chemical composition-of iron, 9 to 27% of chromium, 4 to 8% of nickel, and 0.2% or less of carbon.
The stainless steel has a plurality of fine pores formed by sintering of powder material having a hardening property, and the plurality of fine pores have a porosity of 15% or less.
A manufacturing method of rotary compressor of the invention comprises:
(a) a step of Preparing a cylinder,
(b) a step of preparing a roller,
(c) a step of preparing a vane,
(d) a step of presenting a refrigerant, and
(e) a step of assembling the cylinder, roller, vane, and refrigerant.
The step of preparing the vane further comprises:
(i) a step of molding a stainless steel powder material into a specified shape, land forming a molded piece,
(ii) a step of baking the molded piece and forming a base molded piece having fine pores, in which the fine pores have a porosity of 15% or less,
(iii) a step of heating the base molded piece, and forming a base molded piece having martensitic structure, and
(iv) a step of nitriding the base molded piece having the martensitic structure and fine pores, and placing a nitrogen diffusion layer and an iron-nitrogen compound layer on the surface of the base:molded piece. In which, the nitrogen diffusion layer is formed on the base molded piece, and the compound layer is formed on the nitrogen diffusion layer.
In this structure, the wear resistance of the vane is extremely improved. Further, the dimensional distortion of the vane is decreased. In addition, strength lowering and brittleness of the vane are lessened. As a result, the long-term reliability of the rotary compressor is extremely enhanced.